Endophthalmitis is a potentially blinding complication of ocular surgery and globe penetrating injury. The numbers of cases, as well as the rate, has risen in recent years because of the increasing numbers of cataract surgery cases, increasing age of patients, and potentially increasing resistance of microbes to prophylactic measures and their ability to form biofilms on new lens materials. Antibiotic resistance among Staphylococcus aureus and Enterococcus faecalis has become an issue of considerable public health concern. This competing renewal aims to continue research that has led to the delineation of specific roles of bacterial toxins and host factors in the pathogenesis of endophthalmitis. A new Co-PI brings additional insights and experience on the host response to the project. The central hypothesis is that after microbes enter the anterior chamber, bacterial load or virulence traits foil antimicrobial factors and clearance mechanisms in the aqueous. Microbes then use the same or other virulence traits to promote translocation through the capsule into the posterior segment. In the posterior segment, limited vitreous flow and antimicrobial defenses lead to an overwhelming infection and vision loss stemming in part from interference with normal host cell defense mechanisms. This hypothesis will be tested by 1) Determining how virulence traits alter trafficking of bacteria entering the eye through the anterior chamber; 2) Determining how virulence traits foil innate defenses including 2-defensin antimicrobial activities; 3) Identifying the cells first to respond in the anterior and posterior segments to infection; determining the mechanism for detection of invading gram positive bacterium; and determining whether virulence traits affect detection or response; and 4) Determining how an antiapoptotic factor, 1B-crystallin, is cleaved during S. aureus endophthalmitis, which correlates in preliminary studies with retinal damage. PUBLIC HEALTH RELEVANCE: Endophthalmitis frequently leads to vision loss, despite aggressive antimicrobial therapy and surgery. This problem is exacerbated by increasing antibiotic resistance of the offending microbe, and the increasing age of the patient population. Antibiotic resistance among Staphylococcus aureus and Enterococcus faecalis is now an issue of considerable public health concern. Understanding which bacterial and host factors play critical roles in the pathogenesis of endophthalmitis will permit new therapeutic approaches and preventive strategies to be developed, preserving vision for many patients undergoing cataract extraction or other ocular surgery. It may also have the extrinsic value of leading to new strategies for the treatment and prevention of antibiotic resistant infection at other sites as well.